Carbonic anhydrase (EC 4.2.1.1) is a globular zinc metalloenzyme of molecular mass 30,000. The enzyme was discovered in 1933 and has been the subject of intense scientific investigation. Multiple isoforms have been discovered in plant and animal. The enzyme also exists in plant tissues where it is believed to facilitate the transport of carbon dioxide. Red blood cells contain isoenzymes I and II, which are among the most active. Carbonic anhydrase II has among the highest molecular turnover number of known enzymes. One molecule of carbonic anhydrase II can hydrate a million molecules of carbon dioxide in one second. Physiologically, carbonic anhydrase facilitates the removal of carbon dioxide from the mammalian body, among other functions. The general enzyme reaction is shown below in equation 1.CO2+H2O<=>HCO3−+H+  Equation 1
Carbonic anhydrase has been used in many studies directed at improving or testing of various methods of protein immobilization. The high turnover rate of the enzyme renders it an ideal protein for these types of experiments
The presence of carbonic anhydrase in solution facilitates the transfer of carbon dioxide from the gas to the liquid phase and from the liquid phase to the gas phase. This effect is based on the well established laws governing the mass transfer of gases. The management of carbon dioxide has begun to attract the attention of the scientific community, due to the problem of global warming, to the need for fresh water via desalination of ocean and sea water, and to the use of artificial lung machines.
Carbon dioxide emissions have been identified as a major contributor to the phenomenon of global warming. Carbon dioxide is a by-product of combustion and it creates operational, economic, and environmental problems. It is a reaction product without any fuel value, and is an environmental concern since it is the principal greenhouse gas. In addition, because it is an acid gas, carbon dioxide forms carbonic acid in the presence of water, which is corrosive in nature. The removal of this greenhouse gas from the exhaust stream of fossil-fueled industrial processes is a major ecological and economic issue. Moreover, there are few current practical processes for removing carbon dioxide from gaseous streams. As one example, a current process for the removal of carbon dioxide from gaseous emissions purifies the carbon dioxide to a high concentration (e.g., 70 100%), compresses it, and injects it into oil wells as a compressed gas. However, the compressed and highly concentrated toxic carbon dioxide has the potential to escape back into the air. Thus, no method or device for removing carbon dioxide from the exhaust stream of fossil-fueled power plants exists which satisfies the needs of safety, efficiency, and economy. There is often a need to remove carbon dioxide species, including bicarbonate and carbonate and carbonic acid, from solution. For example, in an artificial lung, the vital process is the removal of these carbon dioxide species (defined as carbon dioxide, bicarbonate, carbonate, and carbonic acid) from blood. In the desalination of ocean and sea water, the elimination of carbon dioxide species and recycling of the resulting carbon dioxide is important. See the following U.S. Pat. Nos. 7,083,730, B2; 2005/0145568 A1; 7,459,088 B2; 2009/0297431 A1; US 2010/0108587.
Previous interest in carbon dioxide has been centered around the use of the gas in a variety of the processes. Prior art processes for the management of carbon dioxide are described in the following U.S. Pat. Nos. 3,659,400; 3,853,712; 4,032,616; 4,047,894; 4,162,298; 4,452,676; 4,521,387; 4,710,362; 5,061,455; 5,112,740; 5,609,838; 5,618,506; 5,624,812; 5,565,319; 5,674,463; and 5,690,099.
Also known in prior art, there is the process disclosed in WO 96/40414 in the name of Trachtenberg. Trachtenberg discloses a process for gas separation wherein a selected gas in a mixed gas strew is contacted by an enzyme having an active site directly contacted by the mixed gas stream, and the selected gas is at least partially removed from the mixed gas stream.
EP511719 discloses a process where carbon dioxide is being removed from a gas stream using a enzyme reactor in which carbonic anhydrase is immobilized on a porous substrate.
Moreover, the United States Air Force carried out two investigations in 1965 and 1966 and the possible use of carbonic anhydrase to remove carbon dioxide from space vehicles. The first study explored the absorption of carbon dioxide from an air stream using a closed air loop apparatus. A variety of chemicals alone and/or in combination with CA were evaluated, with respect to their capacity to remove carbon dioxide. The principle conclusion drawn was that the closed air loop system provided an adequate method to study the removal of carbon dioxide from a stream of air. The second study was directed at determining the efficiency of carbon dioxide removal from an air stream using carbonic anhydrase in the presence of various amines. The conclusion reached was that the amine solutions could possibly be used for carbon dioxide absorption and desorption in atmosphere control concepts.
Although many studies relating to the management of carbon dioxide have been conducted in prior art, there is still presently a need for a process and an apparatus that will efficaciously manage carbon dioxide rapidly and at a relatively low cost either for producing carbon dioxide or removing it from a CO2-containing gas.